1. Field of the Invention
The present invention relates to an inkjet printer system and an ink supply apparatus.
2. Discussion of the Background
An inkjet printer is an apparatus which forms images of information such as characters, graphics, patterns, and photographs on a print surface by ejecting fine particles of ink from a plurality of nozzles, which are formed in a print head, to deposit the ink on a print medium while moving the print head relative to the print medium. In the inkjet printer, since ink is consumed according to the ejection of the ink, a carriage of the print head or a printer body is provided with an ink tank (ink cartridge) having a volume based on the intended use. In case of a large-sized inkjet printer for printing commercial advertisements, banners, and the like, a large amount of ink is consumed in a relatively-short time. In such an industrial inkjet printer, therefore, a large volumetric ink tank is generally provided in the printer body, and the ink tank and the print head are connected through tubes or the like so as to supply ink from the ink tank to the print head according to the ejection of the ink.
As the inner pressure of the print head becomes higher than the normal atmospheric pressure, a problem that ink is pushed out of nozzles to drip onto a print medium, i.e. a dripping problem occurs. To solve this problem, in the inkjet printer, the ink supply device is adapted to control the inner pressure of the print head to be slightly lower than the normal atmospheric pressure, i.e. slight negative pressure. As one of conventional ink supply devices, there is known an ink supply device which includes an ink tank (main tank) disposed on a printer body and a sub tank of a smaller volume disposed between the ink tank and a print head on a carriage, and which is of a “negative pressure producing type” in which the print head is made into a slight negative pressure by reducing the pressure of the sub tank (see, for example, JP-A-2004-284207 and JP-A-2006-62330). Generally, inkjet printers including such inkjet printers having the ink supply device of the aforementioned type have the following problem. That is, as the inkjet printer is continuously used for a long time or has remained in the nonoperating state for a long period of time, ink and dust stick to nozzle peripheries of the print head, thus not allowing the ink to be ejected properly. For solving this problem, there is an inkjet printer which includes a suction route for forcibly sucking ink remaining in the print head in the state that the nozzle face of the print head is capped by a rubber cap, for example, on start-up (for example, see JP-A-2007-216535). By forcibly sucking the ink, old ink is sucked and removed and, at the same time, new ink is sucked and supplied from the main tank into the print head, thereby reestablishing the print head to a state that ink can be ejected from the nozzles properly.
The nozzle face of the print head is capped for achieving the suction of ink. However, if there is a displacement between the nozzle face and the rubber cap, suction force may be reduced because air enters through a space between the nozzle face and the rubber cap. In this case, old ink within the print head is sucked and removed, but new ink sucked from the main tank is hardly supplied to the print head so that the print head tends to be in a state containing air bubbles (not filled with ink). Similarly in the print head having the ink supply device of the aforementioned type, air bubbles may exist in the portion connecting the print head and the sub tank and in the print head. If the ink is ejected from the nozzles in this state, there is a problem that it is difficult to achieve stable ejection of ink because defective ejection occurs in which air bubbles not ink are ejected from the nozzles.